The invention relates to cable testing.
The invention has a particular application in association with pulse echo techniques where locating cable faults is carried out by timing the period taken for a test pulse to travel along a cable and an echo pulse to return from the fault. For example in order that the start of the cable does not itself appear as an apparent fault in such testing the equipment must be impedance matched so that there are no echo pulses generated at the junction of the cable and test equipment, assuming there is no fault at this point.
For a general explanation of pulse echo techniques reference can be made to South African patent specification No. 64/4200. In that patent specification or other pulse echo technique arrangements some form of automatic impedance matching is preferably required especially as the matching may vary as different cables are tested. Further, test leads are often required between the testing equipment and the cable and this produces problems in operating the equipment.
However, the invention has more general application enabling the determining of impedance characteristics at selected sections along a length of cable.